SAS men are ordered never to write books

Every member of the SAS and SBS is to sign a personal contract undertaking never to publish details of their unit and the way they do their work without prior permission from the Ministry of Defence.

The plan is the MoD's response to the recent wave of books published by ex-members of the SAS . It fears that further disclosures could not only compromise special forces' tactics but also reveal top-secret operations that the Government would rather not admit to. The ministry said it has not yet decided whether it will also try to get former personnel to sign.

Every serving member of the elite units will be summoned before the Director of Special Forces - an Army brigadier - and told to sign a personal contract. If they refuse, they will be "RTUd" - returned to their former units - the ultimate disgrace for anyone who has passed the demanding six months of selection tests and been "badged" as a member of the Army's Special Air Service, the Marines' Special Boat Service or the RAF Special Forces.

The new contracts involve a "contractually binding, lifelong, civil law obligation not to disclose any information about the work of the UK Special Forces without specific prior authority".

All members of the Special Forces, including 22 SAS Regiment, based in Hereford, and the two Territorial Army SAS Regiments - 21 and 23 SAS - will be required to sign. So will the SBS, who carry out underwater sabotage and reconnoitre enemy coasts, and some members of the RAF.

Civil servants who work closely with the Special Forces are already considered to have an "enforceable duty of confidentiality".

Special forces' personnel are already sworn to secrecy but once they have left the services there is little the MoD can do to prevent them publishing accounts of their experiences. The recent wave of disclosures began when General Sir Peter de la Billiere, the senior British officer in Saudi Arabia during the Gulf war and a former member of the SAS, published a book called Storm Command. In it, he gave details of SAS and SBS operations behind Iraqi lines, including the destruction and capture of an eight- man patrol, Bravo Two-Zero.

Two survivors of the patrol, using pseudonyms, subsequently published their own accounts, which became best sellers - Bravo Two-Zero by Andy McNab and The One that Got Away by Chris Ryan.

Former members of the Special Forces have signed the Official Secrets Act, and are also bound by Queen's Regulations and Crown Copyright. They also face the censure of their former comrades if they break the secretive ethos of the Special Forces.

Even so, the MoD has become increasingly concerned that unauthorised disclosures might take place, and has introduced the new contracts which will be a particular deterrent to potential publishers.

Besides the now well-known operations in the Falklands, the Gulf and Bosnia, British special forces have been extensively involved in Northern Ireland, against drug barons in South and Central America, and may also have worked in the former Soviet Union and Afghanistan.

Nevertheless, MoD sources admit there is still nothing to prevent an ex-SAS man publishing his memoirs abroad, raising the spectre of another Spycatcher fiasco. Last night the MoD said: "We will certainly seek to enforce the contracts wherever in the world we can".

Should an ex-member of the Special Forces break the contract, however, it is debatable whether a civil court would rule in the MoD's favour, given the difficulty of getting witnesses to testify.